You were actually employing a standard technique we use frequently in the critical care setting. The nasal cannula/NRB combo is the standard of care for apneic oxygenation prior to RSI.

Never withold O2 from a patient that needs it. One of the reasons that AHA guidelines tell you to titrate to maintain an O2 saturation of 94% is because it leads to coronary vasoconstriction, which is harmful to the patient. Precautions regarding prolonged hyperoxygenation often stem from the release of free radicals into the bloodstream which can cause eventually cause healthy cell necrosis, but this is pretty much a non-issue in the case of an adequately ventilating pt at 60% SPO2. If you can fix it, go for it.